Sulfate-Passivated CsPbI₃ Perovskite Nanocrystals for Efficient Red Light-Emitting Diodes

Due to their excellent optical performance, lead halide perovskite nanocrystals (PeNCs) have been widely used in optoelectronic devices. However, the presence of surface defects such as localized trap states severely hampers their practical application in optoelectronic fields. In this work, we have developed a simple method to reduce surface defects by introducing sulfuric acid after the nucleation of CsPbI3 PeNCs is complete. Sulfate ions effectively interact with the exposed metal lead ions on the surface of perovskite NCs, leading to surface passivation. This process represses nonradiative recombination and significantly enhances the luminescence efficiency of PeNCs. Moreover, the passivated CsPbI3 PeNCs with SO42- exhibit a lower overall energy-level structure compared to that of pristine CsPbI3 PeNCs, promoting improved electron injection. Benefiting from this highly effective passivation strategy, light-emitting diodes (LEDs) based on SO42--passivated PeNCs exhibit an optimal external quantum yield of 9.94% and luminance of 2182 cd m(-2), surpassing the performance of LEDs made from pristine PeNCs.